1. Field of the Invention
The present invention relates to a radiation imaging apparatus.
2. Description of the Related Art
There is known a radiation imaging apparatus configured to capture a radiation image based on detection of radiation (for example, X-ray) transmitted through a subject. For example, a digital radiation imaging apparatus including an X-ray phosphor member and a photodetector has advantages such as their good image characteristics and their ability to share image data, which is digital data, in networked computer systems. There is known as the digital radiation imaging apparatus an imaging apparatus including a solid detector in which a phosphor member configured to convert radiation into visible light is stuck on a radiation image detector. In the radiation image detector, a plurality of photoelectric conversion elements including thin film transistors are two-dimensionally arranged.
In the imaging apparatus, as discussed in Japanese Patent Application Laid-Open No. 2002-267758, a drive processing circuit substrate configured to drive an X-ray image detector and a signal processing circuit substrate configured to process output from the X-ray image detector, are disposed on a back surface side and side surface part of a support member having a surface side with the X-ray image detector placed thereon. These circuit substrates and the X-ray image detector are connected via a flexible wiring substrate. In Japanese Patent No. 3880094, a substrate having photoelectric conversion elements and an end face of a phosphor sheet are sealed with a sealing member.
In Japanese Patent Application Laid-Open No. 2008-002987, an imaging apparatus suitable for a mammography apparatus includes a cassette accommodating an image recording plate including a recording layer in which a radiation image is accumulated and recorded. An end face of a portion including the recording layer in the image recording plate is disposed in a dent of a side wall of the cassette.
Japanese Patent No. 4497663 considers protection of a radiation image detection panel from dropping and impact of an imaging apparatus.
Even if radiation is irradiated to a portion between an outer periphery of a range in which the photoelectric conversion elements and phosphor member of the radiation image detector accommodated in a housing of the radiation imaging apparatus overlap each other (a range in which radiation can be detected) and a side surface of the housing, the radiation image cannot be detected. Herein, the range in which the radiation can be detected is referred to as a sensor portion. The portion between the outer periphery of the range in which the radiation can be detected and the side surface of the housing is referred to as a non-sensor portion. Generally, in the radiation imaging apparatus, particularly the mammography apparatus, it is an important issue to reduce the non-sensor portion to minimize a defect in the radiation image. In the imaging apparatus of Japanese Patent Application Laid-Open No. 2002-267758, a connection electrode is provided on the outer periphery of the surface of the radiation image detector to connect the flexible wiring substrate to the radiation image detector. Therefore, the photoelectric conversion elements cannot be disposed to extend to the outer peripheral end of the radiation image detector. Furthermore, because the flexible wiring substrate is disposed on the outside of the outer shape of the radiation image detector, the sensor portion cannot be brought close to the side surface of the housing of the imaging apparatus.
Because the sealing agent exists on the substrate having the photoelectric conversion elements and the end face of the phosphor sheet in the imaging apparatus discussed in Japanese Patent No. 3880094, the sensor portion cannot be brought close to the side surface of the housing of the imaging apparatus. In the imaging apparatus discussed in Japanese Patent Application Laid-Open No. 2008-002987, only a small gap exists between the radiation image detector and the side wall of the cassette. Therefore, when a fragile substrate such as a glass plate is used as the image recording plate, breakage of the radiation image detector caused by contact or collision to the side wall of the cassette cannot be sufficiently prevented.
Since a buffer means is disposed between a base having a surface having the radiation detection panel disposed thereon and the side wall of the housing in the imaging apparatus discussed in Japanese Patent No. 4497663, the sensor portion cannot be brought close to the side surface of the housing of the imaging apparatus.